La1-xSrxMnO3 powders were prepared by auto-ignited combustion of poly(ethylene glycol) (PEG)-metal-nitrate gel precursors. The thermal behaviour of the precursors strongly depends on the ratio of PEG to metal nitrate, which is closely related to the ratio of fuel to oxidizer. The burning behaviour in a furnace was successfully explained by valence concepts normally encountered in propellant chemistry. The formation of a pure perovskite phase was significantly influenced by the homogeneity of the gel precursor. Perovskite structured oxides were formed through two different paths, one of which was direct formation from the burning of a gel precursor and the other was a subsequent structural evolution by heat treatment after burning. The formation procedure of the perovskite and the morphology of powders could be explained in terms of the burning behaviour of the precursor and the role of organic residue.