Symmetric to asymmetric transitions of laminar-premixed methane-air flames anchoring in symmetric sudden expansion channels are explored. Numerical and experimental studies on flame anchoring phenomena are carried out. Simulations predict attachment of cold flow to one of the side walls (Coanda effect), above a critical Reynolds number. However, with symmetric ignition near the sudden expansion, initially asymmetric cold flow becomes symmetric and a symmetric flame anchors at the sudden expansion. Below a critical value of Reynolds number (Re-C,Re-R), both steady flow and flame are symmetric. When fuel-air mixture is ignited asymmetrically close to the sudden expansion for Re > Re-C,Re-R, both the flow and the flame attach to one of the side walls asymmetrically if the transverse distance of ignition is greater than a critical value. The flow attachment length is always smaller than flame attachment length. Experimentally visualized flame anchoring phenomena for ignition near the exit are in conformity with corresponding numerical predictions.