The bakery chain, which has 1,661 shops in the UK, grew like-for-like revenues by 3.2% in the 26 weeks to June 28. Operating profits due later this month are now on course to be around £16-17 million, up from £11.5 million last year.
The improvement follows a move by chief executive Roger Whiteside to increase the focus of the business on the food-on-the-go market, which accounts for 75% of customer visits, rather than traditional take-home business.
The company has previously admitted it underperformed the food-on-the-go sector as convenience stores, coffee shops and fast food operators better met customer demands, particularly in traditional shopping centre locations.
Greggs has responded by completing 131 shop refurbishments in the first half of the year, in line with its plan to refit around 200 shops this year.
It also opened 26 new shops and closed 36 in a drive to target more sites in locations such as retail and industrial parks and motorway service stations.
Greggs has benefited from comparisons with a period of soft trading last year but adds that growth is also being driven by improvements to its products, availability, service and value.
The company added: "Overall, we expect to deliver an improved financial result for the year and further progress against our strategic plan."
It has introduced a new pizza product that has become one of its fastest selling lines, as well as a range of 'heat to eat' sandwiches. In savouries it has improved the fillings in its best-selling lines such as Steak Bakes.
Cost inflation has also shown signs of easing recently but Greggs has warned that the costs of investing in its turnaround programme is likely to constrain profit growth over the next two years.
Shares opened more than 2% higher today.
Shore Capital analyst Darren Shirley said: "Comparatives for the period were weak and the weather conditions have been almost perfect for Greggs, so we are not getting carried away.
"However, stores have clearly benefited from improved availability, longer trading hours as well as product upgrades.
"We believe Roger Whiteside merits much credit for progressively returning Greggs' stores to like-for-like growth over the course of his 15 months' tenure."