The company - which also owns brands including Garfunkel’s, Joe’s Kitchen and Chiquito - reported an adjusted pre-tax profit of £56.7m in 2017, down from £77.1m.
Sales fell 4.4 per cent to £679.3m and dropped 3 per cent on a like-for-like basis.
Chief executive Andy McCue is overseeing a turnaround which has seen a revamp of pricing, food quality and marketing.
The group is now planning to launch an “extended range of healthy dishes”, upgrading vegetarian and vegan options and introducing a new desserts range as it looks to better compete with rivals.
Mr McCue said: “As expected, 2017 was a transitional year for the group, with significant investments made in price and proposition within our leisure business, which is driving improving volume momentum.
“We start 2018 with a significantly more competitive offering in our leisure business, a strengthened pipeline of growth opportunities in both our pubs and concessions businesses, and a leaner, faster and more focused organisation.”
The results come at an increasingly challenging time for the casual dining sector.
Burger chain Byron and Jamie’s Italian have both undertaken company voluntary arrangements this year, which saw hundreds of jobs lost as dozens of restaurants closed down.
Prezzo is also set to close up to a third of its 300 restaurants as it begins an overhaul that will put hundreds of jobs at risk.
Soaring costs linked to the Brexit-hit pound, the resultant collapse in consumer confidence and rising business rates have combined to hammer the sector, with more pain forecast.
The Restaurant Group also flagged cost pressures including increases in wages, the introduction of the apprenticeship levy and the hike in business rates.
The firm operates 497 casual dining sites across the UK, as well as a raft of concession sites.