Shares in travel company Tui (LSE: TUI) have been a huge disappointment this year. They’ve slumped by around 18% and have shown little sign of mounting any kind of recovery. However, now could be a superb time to buy a slice of them, since the company is expected to deliver improved financial performance over the medium term.

In fact, Tui is forecast to report a rise in net profit of 12% in the current year, followed by an increase in earnings of 15% next year. On its own, this could be enough to rapidly improve investor sentiment and push Tui’s share price higher, but when combined with a low valuation it makes the stock even more enticing. For example, Tui trades on a price-to-earnings (P/E) ratio of just 11.2 which, when combined with its growth forecasts equates to a price-to-earnings-growth (PEG) ratio of just 0.8.

This indicates that Tui’s shares could be due for a major turnaround and with the outlook for the global economy being upbeat, now could be a good time to buy a slice of the company for the long haul.

Call a plumber

Similarly, North America-focused Wolseley (LSE: WOS) could be an excellent long-term purchase, with the world’s largest economy in the midst of a major economic turnaround. This could help Wolseley’s shares to come back from their flat performance of the last year, with them having been down by as much as 18% during the period. And with US interest rates unlikely to increase at a rapid rate over the medium term, Wolseley’s bottom line could benefit from a more favourable economic outlook.

Evidence of this can be seen in Wolseley’s forecasts, with the plumbing and heating company expected to increase its earnings by 8% this year and by a further 12% next year. This puts it on a PEG ratio of only 1.1 and with Wolseley due to increase its dividend by 11% next year, it could become a very appealing income play even though it currently yields a rather lowly 2.5%.

Comeback trail

Meanwhile, shares in Premier Oil (LSE: PMO) have already begun a comeback, with them rising by 52% this year. Clearly, this is at least partly due to improving investor sentiment towards the wider oil sector, but is also as a result of a sound strategy being pursued by Premier Oil in the current challenging circumstances.

For example, it’s cutting costs, becoming more competitive and generating greater efficiencies. This should improve its long-term financial outlook and when combined with an asset base that has been enhanced by the acquisition of Eon’s North Sea assets, Premier Oil seems to be positioning itself for future growth.

Certainly, the share price rise of the last few months may not be repeated in the next few months and a falling oil price would be likely to hurt Premier Oil’s valuation. But for investors who can live with above-average risk, Premier Oil could be a strong turnaround play with high potential rewards.

Despite this, there's another stock that could be an even better buy. In fact it's been named as A Top Growth Share From The Motley Fool.

The company in question could make a real impact on your bottom line in 2016 and beyond. And in time, it could help you retire early, pay off your mortgage, or simply enjoy a more abundant lifestyle.

Click here to find out all about it - doing so is completely free and comes without any obligation.

Peter Stephens owns shares of Wolseley. The Motley Fool UK has no position in any of the shares mentioned. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.